Been lots of conversation about each type of fixture in the past in general or specific. Might do some research into fixture maintinence or divide the question up into each as a topic because each needs different things looked at. PAR's for instance often need grounds tightened and a verification of the tension of the lamp base that will hold the lamp with a bounce amongst wiring things and or can itself concepts. Fresnels... wiring and inspection of the socket as with Lekos all needing cleaning but in different ways. This much less inspection of loose screws, tightening of them at times with supplements and cleaning - dish washer clean or not (another thing to research the dish washer.) Various oils etc. Lots out there on how to or need to refine each fixture you would work on.